Markery molekularne wykorzystywane w selekcji zwierząt hodowlanych

Selekcja i dobór osobników do kojarzeń jest istotnym etapem pracy hodowlanej. Jednym z najstarszych i najbardziej powszechnych kryteriów decydujących o wyborze zwierząt do dalszych kojarzeń są cechy fenotypowe. W celu osiągnięcia lepszych efektów hodowlanych, klasyczną selekcję coraz częściej uzupełnia się wynikami badań wykorzystującymi markery molekularne powiązane z cechami użytkowymi. Pierwotnie stosowane markery były oparte na polimorfizmie losowo amplifikowanych fragmentów DNA i polimorfizmie długości fragmentów restrykcyjnych. Rozwój technik molekularnych i genomiki pozwoliły na pełniejsze zrozumienie podłoża genetycznego cech użytkowych i tym samym na wprowadzenie bardziej informatywnych technik opartych na polimorfizmie sekwencji mikrosatelitarnych, jak i wielkoskalowych analizach genomowych wielu tysięcy polimorficznych nukleotydów. W pracy przedstawiono najczęściej wykorzystywane markery molekularne, scharakteryzowano zasadę ich oznaczania oraz przedstawiono przykłady ich zastosowania w naukach zootechnicznych.

Selection plays a crucial role in animal breeding. The oldest and still used methods of selection of animals to further breeding are often based on the phenotypic traits. This approach allows to improve results of breeding in relatively slowly pace and only in narrow degree. More effective way of obtaining progress is involving of molecular techniques and markers into breeding programs. There are many types of molecular markers associated with traits that are important from the viewpoint of the breeders as well as consumers. The most primary molecular markers are based on the proteins but their effectiveness is not sufficient. Therefore polymorphisms present in the genetic material were consider as a better way of enhancing of breeding results. The milestone in molecular biology was developing of PCR technique. Amplification of genetic material open new possibilities in many branches of science but also industry and agriculture. In this way such techniques as RAPD – Random Amplification of Polymorphic DNA, or RFLP – Restriction Fragment Length Polymorphism, were established. Whereas RAPD is mostly used to analysis of genetic diversity between populations, RFLP technique enabled investigating of association between particular alleles and the productive traits. Constant progress in molecular biology brings even more informative methods from polymorphic microsatellite markers up to high-throughput sequencing revealing whole genomes. Microsatellite polymorphism is based on the STR sequences (Short Tandem Repeats) that exhibit considerable variation between individuals, therefore they are great tool to monitoring of genetic structure of breeding population, designing of breeding programs and protecting against the inbreeding depression. Sequencing techniques are focused on the SNP polymorphism (Single Nucleotide Polymorphism), appearing between genomes. Sanger sequencing is limited to analysis of relatively small sequences, whereas NGS techniques allow to screen whole genomes in searching of polymorphic nucleotides involved in expression of desire traits. Results of sequencing are used to designing and development of SNP panels, that enable simultaneous screening of huge number of polymorphic nucleotide. Modern breeding programs are often supplemented by the results of genomic analysis, that brings meaningful insight into genetic background of such traits as meat quality, milk production or reproduction traits. Constant development of technology is followed by the decreasing of costs and therefore it seems that breeding programs assisted by molecular markers will be more widely introduced into the common usage.